Although a significant health concern for all Americans, overweight/obesity disproportionately affects Mexican- Americans. To reduce the risk of obesity-related chronic diseases in adulthood, it is critical to intervene in childhood. Th transition from childhood to adolescence is a particularly important period because adolescent obesity is a strong risk factor for severe obesity in adulthood, a risk that is amplified for Hispaic males. Intervention efforts to reduce caloric intake and increase physical activity, however, have been only modestly successful. To better understand obesity and improve prevention/intervention outcomes, it is necessary to identify distal factors that increase risk of obesity, in addition to the more proximal causes of diet and exercise. To address this need, the present research will identify distal causes of obesity across multiple levels of functioning durin a critical developmental period - the transition from childhood to adolescence - in Mexican-origin youth. This proposal requests funds to analyze existing longitudinal data on environmental, family, and child factors that may increase risk of/promote resilience to obesity and excess weight gain across this transition. The proposed research will capitalize on data already collected from the California Families Project (CFP), a longitudinal study of 674 adolescents of Mexican origin and their parents. The purpose of the CFP is to identify risk and protective factors for substance use initiation in Mexican-origin adolescents. The proposed study addresses critical research questions about obesity that were not part of the parent grant. Starting at age 10, children and both parents completed comprehensive measures of individual, family, and sociocultural development and functioning at yearly assessments, including weight, height, and pubertal status of the child. A total of seven years of annual assessments are available for analysis. Hierarchical linear modeling will be used to model the trajectory of weight gain across adolescence. The aims of this research are (1) to identify aspects of the economic (family income, financial stresses), built (density of fast food, distance to parks), and social (neighborhood disorder, discrimination) environment, family factors (parenting, parents' BMI, depressive symptoms, personality), and child factors (child's depressive symptoms, personality) that increase risk of obesity and excess weight gain across the transition from childhood to adolescence in Mexican-origin youth, (2) to examine whether family and child factors regulate the risk of environmental determinants of excess weight gain and obesity, and (3) to decompose the effect of child and parent acculturation on risk of adolescent weight gain and obesity. Identifying distal causes of obesity will provide unique insights into the development and progression of obesity in adolescence and suggest novel targets for intervention efforts.